1. Field of the Invention
Embodiments of the present invention relate in general to recording and/or reproducing apparatuses, e.g., an optical disc player, compensating for a tilt/skew, and method and media thereof. More specifically, embodiments of the present invention relate to an optical disc player compensating for a tilt/skew using an RF envelope detected from an optical disc, and methods and media thereof.
2. Description of the Related Art
As computers become prevalent in every part of our daily lives, the need has increased for as many peripherals and components as possible to increase the effectiveness and the performance of computers. Particularly, diverse types of auxiliary storage media are available, e.g., storing programs and stored data of the computer's memory in the event of computer power supply cut-off. Typical examples of the auxiliary storage media include magnetic storage media and optical disc storage media.
The magnetic storage media, such as floppy disks and hard disks use a magnetic field to record data. However, the capacities of such magnetic storage media are so small that multiple magnetic storage media have to be used to store multimedia data now being generated. To increase the storage capacity of the magnetic disc, an optical disc (or a laser disc) with a relatively large storage capacity and high data retrieval speed has been developed and is now in use. The optical discs can include CD-ROMs and DVDs (digital video discs), for example.
The optical disc is a recording medium recording data thereon or for playing back (reproducing) data therefrom by applying an optical operation. The optical disc has a support base on which data (i.e., data bits ‘1’ or ‘0’) is recorded by laser beams in pit trains on a track, for example. This data can generally accessed or retrieved by detecting a reflected light or an incident light obtained from the illumination with the laser beam, for example.
To record/reproduce data stably on/from a high-density optical disc such as a DVD-ROM, the optical axis of the laser beam emitted onto the optical disc is usually desired to be perpendicular to the surface of the optical disc, that is, the declination angle of the optical axis is perpendicular to the surface of the optical disc. In practice, however, the surface of the disc is sometimes distorted or tilted, and a skew may occur to the optical pickup unit that emits the laser beam. When this occurs, the emission angle of the laser beam (signal) is not perpendicular. As a result, jitter occurs during the reproduction of data. Jitter is a time-based error caused by the vibration of data signals reproduced from the recording medium. Jitter can cause deteriorations in the processing capability of a control unit or a substantial loss of data in a synchronized network due to the lack of processing capability for reproduced signals. Therefore, it is best to reduce the amount of jitter as much as possible.
FIG. 1 is a graph illustrating a relationship between the amount of jitter and the tilt/skew in a related art optical disc player. Here, to set an optical tilt/skew the amount of jitter is measured in a given range while changing the tilt/skew. The changes in the amount of jitter is reflected in the graph of FIG. 1. Therefore, it is possible to adjust the tilt value or the skew value to the point that the jitter is reduced to a minimum.
However, for the compensation of the tilt/skew in the related art optical disc player the jitter measurement had to be done separately. In other words, a certain amount of data was needed to measure jitter, and for a more reliable measurement the same interval was played back repeatedly, which consequently caused delays in data reproduction. In addition, because the jitter had to be computed after processing the reproduced data, the operation itself was a burden. And most importantly, an operation system for accurate measurement of jitter was necessary, and the normal function could be performed only for the jitter measurement with high discriminability.
In the meantime, Japanese Patent Laid-Open Publication Nos. 9-212891 and 9-245357 disclose methods for compensating a tilt using a separate tilt sensor. According to these disclosures, the tilt of the optical pickup unit is detected not through the operation of jitter but with the help of the tilt sensor. However, using the tilt sensor means that the light source cannot be installed at the same position with the tilt sensor. As a result, an accurate tilt angle cannot be obtained, and the entire size of the optical disc player is increased.